#include <u.h>
#include <libc.h>
int fd, freq[7] = {
	0x8321,
	0x8321 * 28 / 27,
	0x8321 * 32 / 27,
	0x8321 * 4 / 3,
	0x8321 * 3 / 2,
	0x8321 * 14 / 9,
	0x8321 * 16 / 9
};
struct{
	int amp, attack, release, dur, Δφ, φ, envQ30, envQ15, count, mod, out;
}op[24] = {
	{0x1000, 0x7fff, 0x4ff0, 1, 0x1111}, /* hat */
	{0x3000, 0x7fff, 0xff0, 3}, /* kick */
	{0x300, 0x7fff, 0x3000, 1, 0x111}, /* kick mod */
	{0x3000, 0x5fff, 0xff0, 30, 0x8321}, /* test */
};
uint hat, kick, test;
short delay[32768];
uint dcnt, dlfo;
void
bar(void){
	int i, j, x, n;
	uchar buf[512 * 4];
	uint b;
	for(b = 0x80000000UL; b; b >>= 1){
		if(b & hat)
			op[0].count = 0;
		if(b & kick){
			op[1].Δφ = 0x9999; /* my kick drum looks like this: ⑨ */
			op[1].count = 0;
			op[2].count = 0;
		}
		if(b & test){
			op[3].Δφ = freq[nrand(7)];
			op[3].count = 0;
		}
		for(n = 0; n < 12; n++){
			for(i = 0; i < nelem(op); i++){
				if(op[i].count++ < op[i].dur)
					op[i].envQ30 += (op[i].amp - op[i].envQ15) * op[i].attack;
				else
					op[i].envQ30 -= op[i].envQ15 * op[i].release;
				op[i].envQ15 = op[i].envQ30 >> 15;
			}
			op[1].Δφ = op[1].Δφ * 0x6fff >> 15;
			for(i = 0; i < sizeof buf; i += 4){
				op[0].mod = op[0].out * 255; /* hat */
				op[1].mod = op[2].out; /* kick */
				op[2].mod = op[2].out * 111; /* kick mod */
				op[3].mod = op[3].out >> 1; /* test */
				for(j = 0; j < nelem(op); j++){
					op[j].φ += op[j].Δφ;
					x = (op[j].φ >> 8) + op[j].mod & 0x7fff;
					x = (x * (x - 0x8000) >> 13) * (x - 0x4000) >> 13; /* cubic sine approx */
					op[j].out = op[j].envQ15 * x >> 15;
				}
				dlfo = dlfo + 220 & 4095;
				j = (j - 4096) * (j - 2048) * j >> 14;
				j = dcnt + 100 + j & 32767;
				delay[j] = x = delay[dcnt] + op[3].out >> 1;
				dcnt = dcnt + 1 & 32767;
				x += op[0].out + op[1].out;
				buf[i] = buf[i | 2] = x;
				buf[i | 1] = buf[i | 3] = x >> 8;
			}
			write(fd, buf, sizeof buf);
		}
	}
}
void
main(int i, char**){
	USED(i);
	for(i = 0; i < nelem(op); i++)
		op[i].count = op[i].dur;
	fd = open("/dev/audio", OWRITE);
	if(fd < 0)
		sysfatal("open: %r");
	hat = 0xffffffff;
	kick = 0x88888888;
	while(9)test = lrand(), bar();
	bar();
}